Dracaena kaweesakii differs from Dracaena yuccifolia Ridl. in its habit, with up to several hundred branches, white (brown when dry) leaf sheaths lacking yellow or dark brown pigmentation and blades with a narrow white margin when fresh. The inflorescence axis of Dracaena kaweesakii is tuberculate-villous, and the species lacks a floral stalk above the pedicel articulation. The tepals are cream-green or cream-yellow and the filaments intense orange. The anthers are 1.7-2.2 mm long and the style 2.2-3.3 mm. The ovary is 1.3-2.0 mm broad and develops into and fruits that largely remain brown on the infructescence, turning orange only just before or after falling.

Distribution. Specimens seen from northern, northeastern and central Thailand, but ancedotal evidence exists as to extensive distribution in adjacent Burma (Fig. 4) through oral reports of the Burmese workers at Doi Ang Khang, which is on the Thailand/Burma border.

On limestone rocks from 550-2000 m altitude. In higher mountains on ridge tops (Chan pa krai form) and on the slopes and/or summits where they occur on lower limestone mountains in Loei and Lop Buri Provinces of Thailand. Higher altitude forms tend to be smaller, with fewer branches, a more open crown and smaller leaves, especially when in more exposed habitats. However, trees to ca 8 m in height and diam. and 50 cm DBH can be found in dense montane forest on limestone ridges at high altitude in northern Thailand.

Conservation status.

As indicated in Fig. 4, there are two groups of lowland populations of Dracaena kaweesakii, in Saraburi and Lop Buri (Central Thailand), where we have reports supported by photographs of seven populations in addition to the localities represented by Wilkin et al. 1500 and Sriponamat 2 and 3. It is found near Nong Hin in Loei Province (northeastern Thailand). There are three known localities in northern Thailand; at Doi Chiang Dao and near Doi Ang Khang and Mae Sai. These population locations were imported into GeoCAT ( Bachman et al. 2011; http://geocat.kew.org/ ) and extent of occurrence (EOO) was calculated to be 73, 657 km2, while area of occupancy (AOO) was calculated to be 44 km2 based on a cell width of 2 km. However, anecdotal reports suggest the species is also distributed well into Burma on limestone ridges. The authors have seen populations of 10s to 100s of individuals and we have received reports of seven populations with sizes from eight to 150 mature plants in Saraburi and Lop Buri Provinces, suggesting that there are likely to be a few hundred plants in central Thailand. There appear to be few plants of Chan pa krai on Doi Chiang Dao. Thus it is likely that even including its distribution in Burma there would be less than 2, 500 mature individuals, the threshold for criterion C of EN ( IUCN 2001).

Dracaena kaweesakii is extracted from the wild for use in horticulture in Thailand and is one of the more popular taxa due to its extensive branching. A number of populations are protected by proximity to temples or having been transplanted into their gardens. There is no evidence yet of over-extraction but sustainability studies are needed at population level; the authors have, for example, encountered an alley of vegetation being cleared to remove Dracaena kaweesakii from a limestone karst in Loei Province. Limestone habitats are generally threatened in Thailand by extraction for concrete manufacture, especially those closest to cities such as Bangkok; the populations in Saraburi and Lop Buri are the most vulnerable to this threat. Fires can also be problematic. Thus a preliminary assessment of Endangered (EN B2b (ii, iii, iv, v) C1) based on the criteria of IUCN (2001) is indicated.

Uses.

Used in horticulture in Thailand.

Etymology.

This species is named for our collaborator, friend and co-author Toi (Keeratkiat Kaweesak) to recognise of his extensive knowledge of Chan diversity.

Notes.

As indicated in Table 1, Dracaena kaweesakii differs from Dracaena yuccifolia in both vegetative and reproductive characters. It has up to several hundred branches, while the latter does not exceed about 80. The leaf sheaths are white (brown when dry) and lack the yellow or dark brown pigmentation found in Dracaena kaweesakii. The leaf blades of Dracaena kaweesakii possess a distinctive a narrow white margin when fresh. The inflorescence axis of Dracaena kaweesakii is tuberculate-villous not glabrous to microaculeate, and it lacks a floral stalk above the pedicel articulation; thus the flower is inserted directly at the pedicel apex. The tepals of Dracaena kaweesakii are cream-green or cream-yellow, with intense orange filaments (as opposed to bright white tepals and filaments), the anthers 1.7-2.2 mm long (as opposed to1.0-1.4 mm) and the style 2.2-3.3 mm long (as opposed to 3.4-5.5 mm). The ovary is broader (1.3-2.0 versus 0.5-1.1 mm) and fruits that largely remain brown on the infructescence, turning orange only just before or after falling (dull light red on the infructescence in Dracaena yuccifolia).

Two specimens collected on Hainan Island, How 70949 & Lau 225 may belong to an expanded concept of this species or a morphologically distinct close relative. Both have relatively thin leaves with pale margins and narrow terminal shoots; floral colour and dimensions also appear similar to those of Dracaena kaweesakii (e.g. tepals ca 6.5 mm long), although there are no flowers at anthesis on those specimens. They both differ in possessing glabrous inflorescence axes, up to 5 flowers per glomerule and a stalk above the point of articulation of the pedicel. Neither is Dracaena cochinchinensis as they have been determined. Both specimens possess a few leaves and an inflorescence with a few closed flowers. The taxonomy of Dracaena with free tepals in Hainan needs urgent revision including field-based study of fertile plants, not least to provide conservation status information.

The fruits of Dracaena kaweesakii were said to be dispersed by squirrels at Nong Hin in Loei Province. This may explain the late transition from brown to orange in colour around the time of fruit fall. Other species in Thailand have dull red fruits on the infructescence, bird dispersal appears likely. Field studies are needed to test these hypotheses.